Ball valves

Does anyone know the type/material I need to look for when selecting a ball valve to use as a regulator for my loco.

I need a 35mm valve?

Thanks

Ball valves are not appropriate in this application, they are either fully open or closed and shouldn't be used for throttling applications....l

A needle type valve is what you need to be looking at...

Material wise you need something capable of withstanding the temperatures and pressures...Stainless internals/Bronze bodied?

Sorry John, wrong to make a statement that these valves are not appropriate in this application. Many people use them , myself for one. Control is as fine or coarse as you want to make it. I have used said type of valve in my 5" Brit 'Lookalike' for the last two or so seasons without any issues with control. Wrong to state they are either fully open or fully closed, when operating them the control is almost as good as a needle valve (IMHO) What is needed is a valve capable of withstanding high temperatures and relatively high pressures. Most suppliers will advise on the correct/suitable type to purchase. Plus of course a system of steady control and a steady hand is needed.

Another post from someone who has obviously no experience of the use of the item upon which they are commenting! Why do people do this? It doesnt help anyone at all! I have used these with exceptional success in loco boilers. There are general application types and high pressure/temperature types but the general purpose ones work just fine. I have found the best place to source small valves is Screwfix. They are not a stocked item but they arrive next day priced around 8 squids. There is enough brass to machine a thread that you want and enough material to be able to cut/machine them to suit your application. You have to be a little careful on initial throttle opening as it can be a little fierce until you get used to it. I havnt found a way of removing the ball during machining so be sure to plug it well and clean it thoroughly. They have a lovely smooth action - I wouldnt use anything else!

Some years ago using ball valves as throttle valves / regulators were discussed at length on another steam forum. Many people in the USA reported excellent results with Swagelok high temperature ball valves as throttles on model steam locomotives. As I recall some people reported making a V notch in the ball opening on the side that opens first, to give gentler starts with a small steam flow.

Swagelok also make an excellent high temp plug valve rated for 1000 psi at 400 deg F / 204 deg C, with several fitting threads available. The 1/4" NPT female threaded version is part ss-4p6t4. Many variations of size and threads are available, have a look on www.swagelok.com. The rating info for temps and pressures is plain to see - no guesswork.

I don't have any connection to Swagelok, except that I have specified and used many of their products in industry very successfully for many years.

Edited By Jeff Dayman on 19/02/2014 22:45:27

The comment above is why Ball Valves are not the best valve for regulating with as a very high proportion of flow is admitted for a small part turn of the handle. They are by far the most reliable at sealing well and working after long periods of non use.

To give more control they are now made with triangular holes though the bore rather than just a cylindrical hole but I don't know if they go below 1/2"

When sourcing from places like Screwfix you do need to be sure that the seals are designed for high temperature as one failing and releasing steam whilst driving could be bit of an experience.

EPDM seals are common for water but you might prefer Viton for steam.

Steve

Well I was quite confident in my initial comments that ball valves are not suitable use as throttling valves and I still standby what i said...I have worked in petrochemicals and high pressure gas industry onshore and offshore, all my working life, so what I've learned and have been taught is rubbish!

what do I  know?....nothing....

Edited By John Rudd on 21/02/2014 14:28:45

Ball valves - no problem with steam - this supplier has valves for all accassions

http://www.valves-online.co.uk/acatalog/Brass_Ball_Valves.html

Hi John,

Apologies for the curt responses; we shouldn't assume ignorance just because opinions differ. I am interested in why you think ball valves won't work for throttling purposes.

I ask as others clearly use them for steam with satisfaction. The ball stop valves I recently fitted to our plumbing do an excellent job as static flow regulators on the hot water. The geometry is also essentially the same as in most barrel throttles, which do sterling work in many a small IC engine. They have a clear advantage of providiong no significant obstruiction to flow when fully open - if properly dimensioned.

Finally, unlike gate and many other types of valve, they can't easily be held shut by pressure on one side of the valve.

Is it a reliability/materials issue, something else - or is there a confusion here between globe valves and ball valves?

Neil

The problem is rapid progression 10% movement on the handle gives about 90% flow. Most people who have worked in the process industries appreciate this. Its not that they wont work other types will work better unless you want a digital performance on/off.

Next time i can get on a rig at work with a flow meter i will record flow & against % handle turned and all will be obvious. Unless using valves with triangular valve as my post above Johns.

Steve

The other big advantage with Ball valves over the needle valve, screw down globe valve or  gate valves is the speed at which they can be shut off, In an emergency I would not want to be winding a handwheel several turns to shut off an engine.

J

Edited By JasonB on 21/02/2014 18:08:10

John - I never made any reference what so ever to what you have done in your working life! But the fact remains that you are giving very specific advice about something you clearly have no personal experience of - if you had ever used one in a loco boiler you would not be saying they dont work, and thus regardless of any other knowledge the advice you are giving is incorrect. I maddens me that this happens so very very often on here and I simply dont understand why people do it. There are, in my experience no issues with material or reliability, but I stand to be corrected. I have fitted them to boilers down to 5" gauge and they work fine. Infact I fitted one to the "steel boiler for under £200" project, and look at how many people swore that couldnt be done?

Fizzy,

I accept your comments about my not using a particular valve for a specific application however I do know where they should and shouldn't be used....

As an aside, my working career covered working at power stations where steam at superheated temperatures and high pressures were not uncommon...is 1800 psi high enough?

I'll leave it to everyone else to advise the op on the appropriate selection for his service and needs.......

What does not work at 1800 psi does not mean it won't work at 100psi, the two conditions are completely un related. Ian S C

Hi John, no disrespects to yourself or the career that you work in, but in power stations and the like minimum standards are stipulated for a number of reasons including specifications that are set out by munufacturers, however they don't test and specify every application possible and therefore won't stand by every end use.

When you are in down to earth industrial engineering there are many things that are used that "should or shouldn't" be used for a particalar application, but they work in a safe and ecconomical manner, but the onus is on the person/s who install or use them to be sure that it will not cause harm to others or damage other equipment and property.

If you have a wobbly table, you shouldn't prop the offending leg up with a book, borrowed from the public library, but there's nothing wrong with using one of your own books. Of course you should fix the table or the floor, but you don't have to, if your happy with the way it works.

I agree with Fizzy, when you have done a full test on a loco or the such like, without a biased opinion, you can then say whether they are suitable or not.

When I first started work, the guy I was under showed me a saying on the back of a red match box which he kept on a shelf, and I quote; "Experience is the best form of education" A saying I've never forgotten.

Regards Nick.

Edited By Nicholas Farr on 22/02/2014 10:22:07